Sighting apparatus for attachment to a conventional firearm having a laser for projecting a beam of light onto a target to assist in aiming the firearm. The sighting apparatus permits the laser to be releasably attached to the firearm by providing a shockproof mount which carries the laser and is releasably attachable to an adapter secured to the firearm. To facilitate activation of the laser and yet avoid complications when removing the laser and mount from the adapter, the shockproof mount is provided with a switch mechanism that is activated by a trigger mechanism on the adapter. The sighting apparatus further permits substitution of interchangeable mounts, each carrying a laser, by providing an adapter which has a boresight adjustment mechanism that serves to adjust the position of the laser with respect to the barrel of the firearm. The laser is protected from damage by the shockproof mount which comprises a pneumatic buffer that absorbs recoil energy.